Subsurface current utilizing buoy system

ABSTRACT

A sonobuoy system is described in which the buoy proper is anchored by a slack cable from which an array of hydrophones is suspended. The sonobuoy is deployed beneath the surface and its depth is controlled by varying the attitude of the buoy so that ocean currents, which are present virtually everywhere in the sea, act on the buoy to generate positive or negative lift thereby increasing or decreasing the depth in accordance with a predetermined program or on command. Vanes attached to the buoy augment the lift of the body of the buoy. Attitude is changed by pumping water between fore and aft tanks. Provision is made for bringing the buoy to the surface from time to time to abstract the information which has been gathered.

United States Patent 1191 Stillman, Jr.

111 3,818,523 1 June 25, 1974 1 SUBSURFACE CURRENT UTILIZING BUOY3.604.386 9/1971 Turci 114/125 SYSTEM 3.633.508 1/1972 Ribberink 102/137' J] Inventor ISqttgJhen L Stillman, Jr l-lolhs Prlmary Exammer TrygveM. Bhx

Assistant E.raminerGregory W. OConnor 1 Assigneer Sanders so ates, c shuAtt0rney, Agent, or Firn1L0uis Etlinger; William L.

Hunter [22] Filed: Oct. 18, 1971 [21] Appl. No.: 190,019 [57] ABSTRACT Asonobuoy system is described in which the buoy [52] U.S. Cl 9/8 R,114/16 E proper is anchored by a slack cable from which an [51] Int. Cl1363b 21/52 r y of hy roph nes is suspended. The sonobuoy is 58] Fieldof Search 9/8; 114/16 E, 235 B; dep oyed neath he surface and its depthis con- 244/33; 102/13, 14 trolled by varying the attitude of the buoyso that ocean currents, which are present virtually every- [56]References Cited where in the sea, act on the buoy to generate positiveUNITED STATES PATENTS or negative lift thereby increasing or decreasingthe depth in accordance with a predetermined program or Jack ll4/O.5 Ton Command vanes attached to the y augment 218E577 5/1954 Diry 114/16 Ethe lift of the body of the buoy- Attitude is changed by 2.892.4016/1959 Michelson 102/14 P p Water between fore and aft tanks- Provision2.972.972 2/1961 Allen 114/16 E s made r ringing thebuoy to the surfacefrom time 3.157.145 11/1964 Farris et a1 114/16 E to time to abstractthe information which has been 3.299.398 l/1967 Hersey et al... 9/8 Rgathered 3.312.902 4/1967 Dean et 211.1 9/8 R 3.382.514 5/1968 Boscov9/8 R 24 Claims, 11 Drawing Figures ACOUSTIC GAS STORAGE RECEIVER T A NK CONTROL INFLATABLE ACCELEROMETER PROGRAMMER VALVE B AG ld VENT 7s 9596 I M OT 0 R PRESSURE COMPARISON CONTROL SENSOR ClRCUlT clRculT l IPATENTEUJIIIIZSIQM 3,818,523,

SHEEI 1 or 2 III/\- ACOUSTIC GAS 109 STORAGE RECEIVER TANK v f f 4lACCELEROMETER PROGRAMMER CONTROL 'NFLATABI-E VALVE BAG I I NT 495 96 5s54 53 PRESSURE COMPARISON MOTOR CONTROL SENSOR CIRCUIT cmcun' IISUBSURFACE CURRENT UTILIZING BUOY SYSTEM FIELD OF THE INVENTION Thisinvention relates generally to buoys which are deployed in the ocean andwhich contain or to which are attached equipment for detecting variousphenomena and particularly to sonobuoys equipped to detect underwatersounds.

BACKGROUND OF THE INVENTION Typically a sonobuoy is deployed at a knownposition in the ocean and is held there, at or near the surface, by along cable connected to an anchor resting on the bottom. One or moresound sensitive devices are supported, either on the anchor cable or bya separate support, to generate signals in response to incident acousticenergy. Instead of being transmitted continuously, such signals areusually stored by a suitable recorder in the sonobuoy and transmittedfrom time to time to a surface vessel or to a hovering aircraft.Transmission is usually by means of a radio link and accordingly it isnecessary that the sonobuoy, or at least part of it, be above thesurface of the sea during transmission.

Various sonobuoy mooring systems have been proposed. In one arrangement,the entire sonobuoy floats on the surface at all times, held by a longslack cable fastened to an anchor. This arrangement requires that thesonobuoy package and the cable be sturdy enough to withstand theconstant buffeting by surface waves, winds and currents. Additionally,the buoy, being on the surface is subject to ready detection by hostileforces.

In another arrangement, the sonobuoy is held well below the surface by ataut anchor cable. A small surface float, carrying an antenna andperhaps other equipment, is tethered to the main buoy by a slack cable.This arrangement requires substantial positive buoyancy, a strong cable,and a heavy anchor. Although the surface float may be smaller than thesonobuoy, nevertheless it is on the surface and subject to damage and/ordetection.

It is a general object of the present invention to provide an improvedsonobuoy system.

Another object is to provide a sonobuoy which remains entirely below thesurface except during periods of data transmission.

Another object is to provide a sonobuoy which is never exposed toexcessively rough sea surfaces.

Another object is to provide a sonobuoy which will seek and maintain anycommanded depth beneath the surface.

Another object is to provide an arrangement by which the depth of thesonobuoy can be varied from time to time or continuously by apredetermined program or by command.

A more specific object is to provide a sonobuoy the depth of which canbe varied by utilizing the power contained in ocean currents.

SUMMARY OF THE INVENTION In a recent examination of ocean currentdistribution, it was found that virtually nowhere in the first 1,000feet of ocean surface water does the current drop below 0.05 knots,except during tide switching in shelf waters which is only for half anhour or so. The present invention is based on the principle ofutilizing, rather than resisting, such currents. In a preferredembodiment, the buoy is tethered by a slack moor. Its depth beneath thesurface is measured by a suitable sensor such as a pressure sensitivedevice which controls a mechanism for adjusting the attitude of the buoyitself and/or vanes attached thereto thereby varying the lifting forcesexerted and the depth of the buoy. The depth may be maintained at apredetermined fixed level, or varied in accordance with a program, orvaried in response to a command.

BRIEF DESCRIPTION OF THE DRAWING For a clearer understanding of theinvention, reference may be made to the following detailed descriptionand the accompanying drawing, in which:

FIG. 1 is a schematic elevation view of the buoy just after it has beendeployed;

FIG. 2 is a schematic plan view of the buoy;

FIG. 3 is a schematic cross section view taken on the line 33 of FIG.-2;

FIG. 4 is a schematic cross section view taken on the line 44 of FIG. 2;

FIG. 5 is a schematic elevation view showing how the buoy is held by theslack moor in the presense of ocean currents;

FIG. 6 is a fragmentary schematic elevation view showing the buoy on thesurface during transmission with an antenna on top of an inflated bag;

FIG. 7 is a schematic elevation view showing how the cable may be keptoff the ocean floor in the absence of ocean currents;

FIG. 8 is a partial cross section view of the buoy showing the buoyancyand attitude adjusting equipment;

FIG. 9 is a schematic diagram of the initial buoyancy control circuit;

FIG. 10 is a schematic block diagram of the depth control equipment; and

FIG. 11 is a schematic block diagram of a portion of the equipment shownin FIG. 10.

DESCRIPTION OF PREFERRED EMBODIMENT Referring first to FIG. 1 a sonobuoyincorporating the invention is indicated generally by the referencecharacter 21 and includes a housing 22. This figure is not drawn toscale and the invention may be used with many of the standard sonobuoypackages, one of which is about inches long and 7 inches in diameter.The buoy 21 is shown a short time after depolyment by a ship or by anaircraft. Since it initially has a large positive buoyancy, it is, atthis time, at or near the surface 23 of the sea. Before being deployed,it had attached thereto an appendage indicated generally by thereference character 24 and shown in dotted lines in the position asoccupied before deployment. More specifically, the appendage 24 includesa sensor package 25, a cable metering and lock up package 26, a cablestorage package 27, a floatation package 28 and a combined power supplyand anchor package 29.

When the sonobuoy is first dropped into the water, it will, in allprobability, sink beneath the surface momentarily but since it hassubstantial positive buoyancy it will soon rise to the surface. Theappendage disconnects itself and starts falling to the bottom. Thesensor package 25 falls away exposing a plurality of acoustic sensingdevices such as the hydrophones 31 fastened to or suspended from a cable32. This cable includes conductors for carrying power and signalcurrents and is fastened to the housing 22 by means of a bridle 33which, in turn, is fastened near opposite ends of the sonobuoy 21. Sincethe buoy is floating, the descent of the appendage 24 causes the cable32 to pay out until the appendage reaches the bottom. Then the driftingof the buoy 21 pulls additional cable from the storage package 27 andthrough the lock up package 26. It is preferred that the total length ofthe cable be about 30 percent greater than the depth of the water at thepoint of deployment. This can be accomplished simply by predeterminingthe length of the cable or by adjusting the metering and lock up package24 for a length of cable appropriate to the depth at which the buoy isto be deployed. Alternatively, a more complex arrangement by which anadditional 30 percent of cable is payed out after the package hits thebottom may be used but such apparatus has not been shown because it iswithin the skill of those familiar with the art and is not part of thepresent invention. The important thing for present purposes is thatthere be sufficient cable to constitute a slack moor, that is, that thecable extending from the anchor to the buoy 21 have a substantialhorizontal component as shown in FIG. 5.

As shown in FIGS. 1, 2, and 3, the buoy 21 is provided with vanes 36 and37 fastened about amidships of the housing 22 near the top as shown.These vanes are to provide a lift in addition to that provided by thesurface of the housing 22. Preferably they are curved in shape so that,before deployment, they fold flush against the cylindrical surface ofthe housing 22 but are extended as shown after deployment. Suchextension may be done manually or automatically. The important thing isthat they be so extended after the buoy is deployed.

As shown in FIGS. 1, 2, and 4, an additional pair of vanes 38 and 39 isdisposed on the housing 22 near the stern and positioned as shown toprevent alternate vortex shedding, thereby eliminating oscillations inthe horizontal plane as the water currents pass over the buoy 21. Thesevanes are also preferably curved to conform to housing 22 to simplifystorage and handling before deployment.

On the top of the buoy 21 at about the central portion there is aconforming rubber skin or bag 41 in the middle of which is mounted anantenna 42. When the buoy is beneath the surface, the bag 4] lies closeagainst the surface of the housing 22 and the antenna 42 is disposedhorizontally as nearly flush as may be with the top surface of thehousing 22. When the buoy is brought to the surface for the transmissionof data, as will be more fully discussed, the bag 41 is inflated therebyerecting the antenna 42, as shown in FIG. 6. A conductor 43 connects theantenna with the interior of the sonobuoy 21.

If the buoy 21 is to be deployed in regions where slack water is likelyto occur, some precautions should be taken to keep the cable off thebottom of the ocean so that it does not become tangled with anythingshould the buoy drift to a position nearly above the anchor. As shown inFIG. 7, this may be done by making a portion of the cable 45 which isnear the anchor of a buoyant material or by attaching floats to such aportion. This end may be accomplished either by making the cable buoyantin the first place or by storing floats in the package 28 and attachingthem to the cable as the last portion is payed out.

Referring to FIG. 8, there are shown schematicaaly two walls 48 and 49which form, along with the housing 22, fore and aft tanks 51 and 52,respectively. A bidirectional positive displacement pump 53 is mechanically connected to two electric motors 54 and 55. The motor 54 is usedto establish initial buoyancy conditions while the motor 55 is used tovary the attitude of the buoy. It would of course be possible to use asingle motor for both purposes but it is preferred, at present, to usetwo motors, as shown.

One side of the pump 53 is connected by means of a conduit 57 directlyto the interior of the tank 51 while the opposite side is connected bymeans of a conduit 58 to one side of a valve 59, operated by a solenoid61. The other side of the valve 59 is connected by means of a conduit 62to the interior of the tank 52. The conduit 58 communicates with aconduit 63 which in turn communicates with one side of a valve 64,operated by a solenoid 65. The other side of the valve 64 is connectedto a conduit 66 which passes through the housing 22 and communicateswith the open sea. The conduit 57 communicates with a conduit 67 whichis connected to one side of a valve 68, operated by a solenoid 69. Theother side of the valve 68 is connected by means of a conduit 71 to theinlet side of a check valve 72, the outlet side of which is connected bymeans of a conduit 73 to the conduit 62. The check valve 72 will passfluid only in the direction shown, that is from the conduit 71 to theconduit 73 but not in the other direction. The valve 59 is open whilethe valves 64 and 68 are closed in the absence of energization of theirrespective solenoids. Energization of the solenoids closes valve 59 andopens valves 64 and 68.

Also shown in FIG. 8 is a pressure sensor 76 which communicates with theopen sea by means of a conduit 77 which extends through the housing 22.The sensor 76 generates a signal, such as an electric voltage or currentor a mechanical displacement, which is indicative of the pressureincident on the housing 22 which in turn is indicative of the depth ofthe buoy. Additional control equipment, to be more fully described, isshown in block diagram form at 77. The equipment for processing andtransmitting the signal from the hydrophone 31 is shown in block diagramform at 78.

When the sonobuoy 21 is first deployed in the water, it has a verysubstantial positive buoyancy and floats on the surface. After all ofthe cable has been payed out, it is preferred that the buoyancy besubstantially decreased so that it is just slightly buoyant duringnormal submerged operation. This is accomplished by means of the valvingapparatus just described above in connection with FIG. 8 and inconnection with the circuitry of FIG. 9. Operation of this equipmentstarts after the sonobuoy section 24 reaches the bottom and all theextra cable is payed out. At that time, the power supply within thepackage 29 is activated. This power supply may be a radioisotopethermoelectric generator or a battery or other kind of power source andis preferably converted from a low voltage to a high voltage directcurrent for more efficient power transmission up the cable to thesonobuoy 21 where it is reconverted to a low voltage unidirectionalcurrent.

Referring now to FIG. 9, prior to the time the power supply is madeactive there is no voltage in the circuit and the solenoids 61, 65 and69 are de-energized with the result that the corresponding valves 64 and68 are closed while the valve 59 is open. When all of the cable is payedout, the power supply is made active and a voltage appears on conductors81 and 82. A timing circuit 83 is connected to these conductors andoperates, when energized, to put a voltage across a winding 84 for apredetermined time starting immediately. The winding 84 is the operatingwinding of a relay indicated generally by the reference character 85 andwhich includes switches 86 and 87. When the winding 84 is energized, theswitch 87 closes, energizing solenoids 61, 65 and 69, thereby closingvalve 59 and opening valves 64 and 68. One terminal of the motor 54 ispermanently connected to the ground conductor 82 and closure of switch87 energizes the motor to run in such a direction as to cause the pump53 to pump fluid to the right as viewed in FIG. 8. Thus, fluid is drawnthrough the valve 64, the conduits 63 and 58, the pump and the conduit57 to the tank 51 and also to the conduit 67, valve 68, valve 72 andconduit 62 to the tank 52. Since the pump is a positive displacementpump, operation for a predetermined time puts a predetermined quantityof fluid into the tanks 51 and 52 which is divided approximately equallybetween them. This quantity is so predetermined as to give the properbuoyancy to the buoy 21 which is a slight positive buoyancy sufficientto cause the buoy to tend to rise in the absence of water current dragexerted on the cable 32. At the end of the predetermined time, thewinding 84 is de-energized, thereby shutting off the motor 54, andde-energizing the winding 61, 65 and 69 so as to close the valves 64 and68 and open the valve 59. The result of this is that the pump 53 is nowconnected so that it can now pump fluid back and forth between the tanks51 and 52.

Referring now to FIG. there is shown in block diagram form the equipmentwhich, in conjunction with that previously described, controls the depthof the sonobuoy 21. A programmer 94 includes a clock and generatessignal voltages indicative of the desired depth of the sonobuoy atvarious times in accordance with a predetermined time schedule. Forexample, it may be desired that it stay below the surface at a certaindepth for 23 hours of the day and then rise for 1 hour. The voltage fromthe programmer 94 is compared with that of the depth sensor 76 in acomparison circuit 95 which generates an error signal which is passed toa motor control circuit 96 which controls the motor 55 to actuate thepump 53 so as to pump fluid between the tanks 51 and 52 in the properdirection to change the weight distribution of the buoy and consequentlyits attitude and the angle of attack of the ocean currents therebycausing the buoy to rise or descend as directed by the error signal. Itis preferred that the magnitude of the change in attitude be correlatedwith the magnitude of the error signal so that a command to change depthby small amount causes less change in attitude than a command to changedepth by a large amount. To accomplish this, a signal indicative of thenumber of revolutions of the pump 53 is fed back to the circuit 96 whereit is compared with the error signal from the comparison circuit 95.Such feedback could, of course, be electrical but at present is ispreferred to use a simple me chanical converter including appropriategearing, all as shown schematically by the dotted line 97. Any ofvarious comparison and balancing circuits may be used, that preferred atpresent being shown schematically in FIG. 11.

Referring now to FIG. 11, The error signal from the comparison circuitis applied through a summing resistor 101 to a junction 102. Apotentiometer 103 having a grounded center tap has its oppositeextremities connected to voltage sources of opposite polarity. Its wiper104 is positioned by the mechanical connection 97 and is electricallyconnected through a summing resistor 105 to the junction 102. Thevoltage of the junction 102 is the input to a servo amplifier ofconventional construction, the output of which controls the motor 55.

The apparatus is designed so that when the buoy is at the desired depth,the error signal from circuit 95 is zero and the wiper 104 in the centerposition shown. If the buoy is then commanded to change depth, an errorsignal from circuit 95 places a voltage on junction 102 which, throughamplifier 106 and motor 55 causes the pump 53 to rotate. The feedbackpath 97 adjusts the wiper 104 until the voltage balances the errorsignal, whereupon the voltage of junction 102 falls to zero and the pumpstops. As the buoy approaches the desired depth, the error signal fromcircuit 95 decreases, placing a voltage on junction 102 which drives thepump in the opposite direction proportionally reducing buoy verticaltravel velocity until the buoy reaches the commanded depth.

It is to be noted that operation of either motor 54 or motor 55 adjuststhe wiper 104. Therefore, the apparatus is designed and the initialconditions established so that after the motor 54 has concluded itspumping operation to establish the initial buoyancy conditions, aspreviously explained, the wiper 104 is centrally located, as shown.Therefore, before deployment of the buoy, the wiper 104 is positionedaway from the center by an amount indicative of the number ofrevolutions of the pump 53 necessary to pump the predetermined quantityof water into the tanks 51 and 52. Since the pump 53 is a constantdisplacement pump, the quantity of water pumped is directly related tonumber of revolutions which in turn is directly related to the time ofoperation. Accordingly, it is necessary to correlate, in the design, theparameters of the pump 53, motors 54 and 55, the timer 83 and theinitial offset of the wiper 104.

Let us assume that the buoy 21 has been at its programmed depthgathering information for a programmed time, for example, 23 hours, andthat it is to be brought to the surface so as to transmit theinformation. The programmer 94 generates a suitable signal whichoperates through the circuits and other equipment just described toincrease the lift and cause the buoy 21 to ascend. As it reaches apredetermined depth, near the surface, as measured by the sensor 76, theprogrammer 94 operates a control valve 108 so as to open, for apredetermined time, a passage from a tank 109 containing a gas underpressure to the inflatable bag 41 which adds further buoyancy, erectsthe antenna 42, and holds the antenna above the waves after the buoy hassurfaced. At the end of another predetermined time, the programmer 94operates the valve 97 so as to vent the gas from the bag 41 to theatmosphere. The programmer than generates another signal commanding thebuoy to descend to its previous depth, or, for that matter, to adifferent depth.

Also shown in FIG. 10 is an acoustic receiver 111 which may receivesonic signals and override the programmer 94 should it, at any time, bedesired to bring the sonobuoy to the surface. This receiver may, forexample, by a part of a commercially available acoustic command system,one suitable kind being that marketed by AMF, Alexandria Division,Alexandria, Va, and designated model 200.

Waves at the surface of the sea cause an orbital circulation of theunderlying water. Such motion, although greatest near the surface,extends a considerable distance below. As the waves increase in size,the actual motion and the accompanying accelerations likewise increaseand extend further beneath the surface. This phenomenon is utilized toprevent a programmed surfacing of the buoy if the sea is so rough as toprevent reliable transmission of data and/or endanger the buoy. Anaccelerometer 112 is provided which senses the vertical acceleration ofthe orbital motion to which the buoy is subjected as it approaches thesurface. lf such acceleration exceeds a predetermined threshold, asignal is sent to the programmer 94 directing it to override theprogrammed surfacing and to command the buoy to descend.

From the foregoing it will be apparent that applicant has provided anovel system which enables the sonobuoy to be disposed beneath thesurface of the sea for the majority of the time where it is not subjectto buffeting by waves and is not subject to ready detection by theenemy. The sonobuoy can be programmed to go to any desired depth byutilizing the free energy of ocean currents and to stay there for anydesired length of time consuming negligible electric power. During thistime the hydrophones can transmit their signals to the signal equipment78 which, for example, may include a tape recorder and play backequipment as well as necessary radio transmitters all as is well knownto those skilled in the art. When the sonobuoy comes to the surface,

the recorder is played back and the information transmitted to a nearbysurface ship or hovering aircraft. The details of the storage andtransmission of the data from the hydrophones however, are not a part ofApplicants invention and are well knwon to those skilled in the art.

Although a specific example incorporating the Applicants invention hasbeen described in considerable de tail for illustrative purposes, manymodifications will occur to those skilled in the art. It is thereforedesired that the protection afforded by Letters Patent be limited onlyby the true scope of the appended claims.

What is claimed is:

l. A buoy system for deployment in a body of flowing water, comprising,

a housing,

an anchor,

a slack cable interconnecting said housing and said anchor, and

means responsive to a signal for varying the lift produced by the flowof water over the surface of said housing.

2. A buoy system in accordance with claim 1 in which said means forvarying includes means for varying the attitude of said housing.

3. A buoy system in accordance with claim 1 in which said signal isindicative of water pressure incident on said housing, whereby the depthmay be controlled.

. 4. A buoy system in accordance with claim 1 m which said housing, itscontents and the cable have an overall positive buoyancy.

5. A buoy system in accordance with claim 1 which includes vanesattached to the exterior of said housing to increase the lift. 1

6. A buoy system in accordance with claim 1 in which said signal isindicative of depth.

7. A buoy system in accordance with claim 1 in which said signal is anexternally originating command.

8. A buoy system in accordance with claim 1 in which said signal isindicative of acceleration.

9. A buoy system in accordance with claim 1 in which said signal isindicative of vertical acceleration above a threshold level caused bysurface waves.

10. A buoy system in accordance with claim 1 in which said signal isindicative of a predetermined program.

11. A buoy system in accordance with claim 19 in which said programincludes a command to bring said housing to the surface.

12. A buoy system in accordance with claim 11 including means fordetecting a rough condition of the sea surface upon ascent and meansresponsive to the detection of a roughness exceeding a predeterminedthreshold for overriding a command to bring said housing to the surfaceand for commanding said housing to descend.

13. A buoy system in accordance with claim 1 in which said cable isconnected to said housing by means of a bridle fastened near oppositeends thereof.

14. A buoy system in accordance with claim 1 in which said cableincludes conductors for the transmission of data and power.

15. A buoy system in accordance with claim I in which said means forvarying includes means for maintaining said housing at a predetermineddepth.

16. A buoy system in accordance with claim 1 which includes a pluralityof hydrophones supported by said cable.

17. A buoy system in accordance with claim 16 having means including anantenna for transmitting the information received by said hydrophones.

18. A buoy system in accordance with claim 17 in which said means forvarying includes means for bringing said housing to the surface of thewater to transmit said information.

19. A buoy system in accordance with claim 18 which includes a gas tightbag, means for inflating said bag when said housing is on the surfaceand means for mounting said antenna on the upper portion of said bag.

20. A buoy system in accordance with claim 1 in which said means forvarying includes means for varying the distribution of the weight withinsaid housing.

2]. A buoy system in accordance with claim 20 in which said means forvarying includes fore and aft tanks partially filled with water and apositive displacement pump operatively connected to transfer water fromone to the other of said tanks.

22. A buoy system in accordance with claim 1 including means forreducing the buoyancy of said housing after its deployment in the water.

23. A buoy system for deployment beneath the surface of a body offlowing water, comprising,

a buoy having positive buoyancy,

an anchor disposed on the bottom of the body of water, and

9 10 a flexible cable having a length substantially greater the attitudeof said buoy, and lift due to the flow f than the depth of said body ofwater interconnectwater over the surface of said buoy, whereby the ingsaid buoy and said anchor, depth of said buoy is varied. said buoyincluding a pressure sensitive instrument 24. A buoy system inaccordance with claim 23 in for generating a signal indicative of thedepth of which said means for varying includes fore and aft said buoybeneath the surface, I tanks partially filled with water and a pump fortranssaid buoy also including means responsive to said sigferring waterbetween said tanks.

nal for varying the weight distribution of said buoy,

1. A buoy system for deployment in a body of flowing water, comprising,a housing, an anchor, a slack cable interconnecting said housing andsaid anchor, and means responsive to a signal for varying the liftproduced by the flow of water over the surface of said housing.
 2. Abuoy system in accordance with claim 1 in which said means for varyingincludes means for varying the attitude of said housing.
 3. A buoysystem in accordance with claim 1 in which said signal is indicative ofwater pressure incident on said housing, whereby the depth may becontrolled.
 4. A buoy system in accordance with claim 1 in which saidhousing, its contents and the cable have an overall positive buoyancy.5. A buoy system in accordance with claim 1 which includes vanesattached to the exterior of said housing to increase the lift.
 6. A buoysystem in accordance with claim 1 in which said signal is indicative ofdepth.
 7. A buoy system in accordance with claim 1 in which said signalis an externally originating command.
 8. A buoy system in accordancewith claim 1 in which said signal is indicative of acceleration.
 9. Abuoy system in accordance with claim 1 in which said signal isindicative of vertical acceleration above a threshold level caused bysurface waves.
 10. A buoy system in accordance with claim 1 in whichsaid signal is indicative of a predetermined program.
 11. A buoy systemin accordance with claim 10 in which said program includes a command tobring said housing to the surface.
 12. A buoy system in accordance withclaim 11 including means for detecting a rough condition of the seasurface upon ascent and means responsive to the detection of a roughnessexceeding a predetermined threshold for overriding a command to bringsaid housing to the surface and for commanding said housing to descend.13. A buoy system in accordance with claim 1 in which said cable isconnected to said housing by means of a bridle fastened near oppositeends thereof.
 14. A buoy system in accordance with claim 1 in which saidcable includes conductors for the transmission of data and power.
 15. Abuoy system in accordance with claim 1 in which said means for varyingincludes means for maintaining said housing at a predetermined depth.16. A buoy system in accordance with claim 1 which includes a pluralityof hydrophones supported by said cable.
 17. A buoy system in accordancewith claim 16 having means including an antenna for transmitting theinformation received by said hydrophones.
 18. A buoy system inaccordance with claim 17 in which said means for varying includes meansfor bringing said housing to the surface of the water to transmit saidinformation.
 19. A buoy system in accordance with claim 18 whichincludes a gas tight bag, means for inflating said bag when said housingis on the surface and means for mounting said antenna on the upperportion of said bag.
 20. A buoy system in accordance with claim 1 inwhich said means for varying includes means for varying the distributionof the weight within said housing.
 21. A buoy system in accordance withclaim 20 in which said means for varying includes fore and aft tankspartially filled with water and a positive displacement pump operativelyconnected to transfer water from one to the other of said tanks.
 22. Abuoy system in accordance with claim 1 including means for reducing thebuoyancy of said housing after its deployment in the water.
 23. A buoysystem for deployment beneath the surface of a body of flowing water,comprising, a buoy having positive buoyancy, an anchor disposed on thebottom of the body of water, and a flexible cable having a lengthsubstantially greater than the depth of said body of waterinterconnecting said buoy aNd said anchor, said buoy including apressure sensitive instrument for generating a signal indicative of thedepth of said buoy beneath the surface, said buoy also including meansresponsive to said signal for varying the weight distribution of saidbuoy, the attitude of said buoy, and lift due to the flow of water overthe surface of said buoy, whereby the depth of said buoy is varied. 24.A buoy system in accordance with claim 23 in which said means forvarying includes fore and aft tanks partially filled with water and apump for transferring water between said tanks.